The present invention is directed to a printing press unit for printing on a web of material as the web passes through a printing station formed by an impression roll and a printing cylinder.
In a printing press unit, such as a rotogravure, a printing station is formed between an engraved cylinder and an impression roll. The engraved cylinder, along with the ink applicator and doctor blade are mounted on a carriage or cart which is removable from the press with a second or other cart having a new printing cylinder being inserted to enable changing the printing cylinders. An example of such an arrangement is disclosed in U.S. Pat. No. 3,625,145, whose disclosure is incorporated by reference thereto. One difficulty with this arrangement is that the impression roller is mounted for vertical displacement to insure contact with the printing cylinder of different sizes carried by the same carriage. Thus, when changing printing cylinders of different sizes, problems arise because of the change in the length of the web being fed through the press.
Another difficulty with this known type of printing arrangement is that a large number of extra carriages are required for supporting the various printing cylinders that are to be inserted into the press. This increases the cost of operation because of the expense of each of these carriages or carts due to the fact that the carriage or cart includes not only the doctor blade but the assembly for positioning the doctor blade and an assembly for positioning the ink applicator relative to the printing cylinder and the ink pan. In addition, this large number of extra carts that are necessary in order to have a fast changeover require additional space for storage when not being used.